Why does ApiGatewayV2 DomainName in Cloudformation Syntax specify list of Tags, but rejects list in favor of single object?

Question

The JSON config below generates the error message:
Properties validation failed for resource apiDomainName with message: #/Tags: expected type: JSONObject, found: JSONArray

"apiDomainName": {
        "Type": "AWS::ApiGatewayV2::DomainName",
        "Properties": {
          "DomainName": { "Fn::Join": [ "", [ "api.", { "Fn::FindInMap": [ "variable", { "Ref": "env" }, "domain" ] } ] ] },
          "DomainNameConfigurations": [
            {
              "EndpointType": "REGIONAL",
              "SecurityPolicy": "TLS_1_2",
              "CertificateArn": { "Fn::FindInMap": [ "resource", { "Ref": "env" }, "apiCert" ] }
            }
          ],
          "Tags" : [
            { "Key": "managedBy", "Value": "cloudformation" }
          ]
        }
      }

Answer

Hello.

I haven't seen the CloudFormation template you're using, so I don't know the details, but you can use it as follows.  
https://docs.aws.amazon.com/ja_jp/AWSCloudFormation/latest/UserGuide/aws-resource-apigatewayv2-domainname.html

```
      Tags:
        - Key: SystemName
          Value: !Ref SystemName
        - Key: Env
          Value: !Ref Env
```

Why does ApiGatewayV2 DomainName in Cloudformation Syntax specify list of Tags, but rejects list in favor of single object?

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